Usually I connect to internet via Wi-Fi, but when I go to the country on weekend I use 3G.
Usually when I try to establish 3G connection I can't do it:
3G connection switches to turned on but actually there is no connection (no small 3G sign above network level and no internet in browser). Sometimes it happens even in a day of non active period or even less.
As workaround for resolving this problem I enable and disable flight mode: after that in most of cases I can establish 3G connection successfully with internet connection.
P.S: I'm from Ukraine. Noticed same behavior on 2 used carriers.